Transcript Lymphatic System and Immunity

Lymphatic System and
Immunity
Courtney Shelton CST, BA
ST 120
Objectives Day 1
• Discuss the structure and function of the
lymphatic system
• Discuss and locate the thymus gland,
spleen, and tonsils
• Identify diseases and disorders of the
lymphatic system
Immune System
• The “safety net” that protects us from
potentially harmful toxins, disease-causing
bacteria, viruses, and cells in our body that
have turned cancerous.
The Lymphatic System
• We know that the circulatory system
brings many needed substances to cells
and then removes the waste products.
• Some substances cannot enter or return
through the capillary walls, including
excess fluid and protein molecules.
Lymph and Lymphatic Vessels
• This excess fluid and protein molecules
are returned to the blood as lymph.
• Lymph is a specialized fluid formed in the
tissue spaces that is transported by way of
specialized lymphatic vessels to eventually
reenter the circulatory system.
How does lymph form?
• Blood plasma filters out of the capillaries
into the spaces between tissue cells
because of the pressure generated by the
heart. There the fluid is called interstitial
fluid
• Most interstitial fluid goes back into the
capillaries. The remainder of the
interstitial fluid enters the lymphatic
system before it returns to the blood.
Lymph
• The lymph then enters the lymphatic
capillaries which permits excess tissue
fluid and protein molecules to leave the
tissue space.
• What would happen if this fluid was NOT
permitted to leave the tissue space?
Lymphatic Capillaries vs. Blood
Capillaries
• Similar to one another
– Microscopic
– Single sheet of simple squamous epithelium
called endothelium
• Different from one another
– The “fit” between the endothelial cells in
lymphatic vessels is larger to allow larger
substances to pass
– Movement of lymph is one way. Blood moves
in a circular route.
Lymph
• Lymph flows into successively larger and
larger vessels called lymphatic venules
and veins
• Eventually empties into two terminal
vessels
– Right lymphatic duct
– Thoracic duct
Thoracic duct
• Largest duct
• The thoracic duct in the abdomen has a
pouchlike structure used for storing lymph
called the cisterna chyli
Lymph Nodes
• Lymph is filtered by moving through these nodes
as it moves from its origin in the tissue spaces to
the thoracic or right lymphatic ducts and then
into the venous blood.
• Nodes are located in clusters
• Function of nodes is defense and white blood
cell formation
Biological Filtration
• A process in which cells alter the contents of the
filtered fluid to prevent local infections from
spreading.
• Lymph enters the node through 4 afferent lymph
vessels
• Lymph flows through lymph spaces called
sinuses that surround nodules found in the outer
and inner areas of the node
Filtration, cont’d
• In passing through the node, lymph is
filtered so that particles such as bacteria
and cancer cells are removed and
prevented from entering the blood.
• Lymph exits through a single efferent
lymph vessel.
Axillary nodes
• Surgeons remove lymph nodes in the
armpit to ensure the removal of any
cancer cells that may have been filtered
out of the lymph drained from the breast.
Thymus
• Small lymphoid tissue organ located in the
mediastinum, extending upward into the
neck
• Largest at puberty
• Plays a critical role in the body’s vital
immunity mechanism
Thymus
• It is a source of lymphocytes before birth
and is then especially important in the
development of T cells
• Completes most of its work in early
childhood and is then replaced with fat and
connective tissue in a process called
involution.
Tonsils
• Located in a protective ring under the
mucous membranes in the mouth and
back of the throat
• Help protect against bacteria that may
invade tissues in the area around the
openings between the nasal and oral
cavities
Tonsils
• Palatine tonsils are on each side of the
throat
• Pharyngeal tonsils a.k.a adenoids are near
the posterior opening of the nasal cavity
• Lingual tonsils are near the base of the
tongue
Spleen
• Largest lymphoid organ in the body
• Located high in the upper left quadrant of
the abdomen lateral to the stomach
• Blood enters the spleen then flows through
dense, pulplike accumulation of
lymphocytes
Function of the Spleen
• As blood flows through the pulp, the
spleen removes by filtration and
phagocytosis many bacteria and other
foreign substances, destroys worn out
RBC’s and salvages the iron found in
hemoglobin for future use, and serves as a
reservoir for blood that can be returned to
the circulatory system when needed.
Questions????